X-ray units



April 18, 1961 G. w. STEEN 2,980,800

X-RAY UNITS Filed July 24, 1958 2 Sheets-She et 2 43 44 FIG. 2

FIG.3

35 FIG. 4

INVENTOR.

GOTTFRID W. STEEN AGEzT 2,980,800 X-RAY UNITS Gottfrid W. Steen,Stamford, Conn., assignor, by mesne assignments, to The MachlettLaboratories, Incorporated, Springdale, Conn., a corporation ofConnecticut Filed July 24, 1958, Ser. No. 750,764

4 Claims. (Cl. 250-90) This invention relates to improvements in X-rayunits adapted for use in radiographing annular sections of hollowbodies, and has particular reference to a new selfcontained X-ray unitwhich is capable of producing, in a single exposure, a high qualityradiographic picture of an entire weld, for example, of a pipe line.

When using a self-contained X-ray unit for radiographing the annularwelds of a pipe line it is highly desirable. to employ in the unit anX-ray tube which generates an X-ray beam extending throughout a radiusof 360 completely encircling the unit. Such a 360 tube can thus beexpected to radiograph the entire circumferential weld of a section ofpipe line when inserted within the pipe substantially on the axisthereof and operated in that position.

In using a unit of this type it is'necessary to drag or propel the unitsubstantially along the axis of the pipe to a point where a weld to beradiographed lies within the annular field of radiation. Therefore,electrical extensions or leads connecting the tube and associatedcomponents or devices to sources of electrical energy must likewise bepropelled or dragged along with the unit. This provides a seriousproblem in units wherein electrical devices are mounted adjacent the endof the tube opposite the end nearest the electrical supply because insuch cases electrical conductors to the devices must necessarily passthrough the field of radiation. Radiographs produced by such units willcontain images of the conductors, which images may obscure some of thedetails of the image of the radiographed welds, or in any event may leadto confusion in a latter study of the radiographs.

The present invention overcomes this objection by providing a novelconductor which is transparent to the X-radiation which it intercepts.This is accomplished by making the conductor of material and dimensionsselected according to the materials and dimensions of other elements,such as windows, through which the X-ray 'beam passes, so that X-rays ofthe particular wave lengths which would normally have been absorbed bythe conductor are absorbed by the other elements before the beam reachesthe conductor, whereby the conductor is transparent to substantially allthe X-rays which it intercepts. I It is, accordingly, a primary objectof this invention to provide a new and improved self-contained X-rayunit producing high quality radiographs of selected subjects which iscompact, sturdy, light in weight, and reliable in operation.

Another object is to provide a novel radiographic -X-ray unit whereinthe component parts are located in positions where they may operate atgreatest efiiciency without interfering with the radiographic process.

Another object is the provision, in an X-ray unit of .the characterdescribed, of suitable means for air-cooling lthe X-ray tube.

a Another object is to provide an X-ray unit of the Patented Apr. 18,1961 above character wherein electrical conductors which are located inthe path of the X-ray beam are so constructed and arranged that they aresubstantially indistinguishable in the radiographs produced by the unit.

Other objects and advantages of this invention will become apparent fromthe following description taken in connection with the accompanyingdrawings, wherein Fig. 1 is an elevational view of an X-ray unit withthe housing partially removed to disclose the invention;

Fig. 2 is an enlarged sectional view of a portion of the interior of theunit;

Figs. 3 and 4 are enlarged front. and side elevational viewsrespectively of an electrical conductor used in the unit; and

Fig. 5 is a graph illustrating certain characteristics of the invention.7 Referring to the drawings, and more particularly to Fig. 1, the deviceincludes a housing 10 which is formed of two cylindrical sections, aforward section 11 and a rear section 12, which are joined at one end incoaxial relation and are closed at their other ends. The rear section 12has a relatively rigid and sturdy end wall 13 and the side wall or shell14 thereof is formed of thin sheeting of aluminum or other selectedmaterial having relatively good X-ray transparency characteristics.

Upon the inner surface of the end wall 13 is an annular bracket 15 whichserves to support an X-ray tube 16 within the housing. The cathode end17 of tube 16 extends outwardly through end wall 13. The opposite 'endof the tube constitutes a hollow anode-supporting portion 18 to which issealed one end of an annular window 19 formed of thin nickel tubing orother selected X-ray transparent material. The anode 20 is sealed to theopposite end of the window 19.and has in it a target 21 formed oftungsten or other selected material which is capable of emitting copioussupplies of X-rays when bombarded by electrons in the manner of aconventional X-ray tube. Window 19 encircles the target 21 and X-rayswhich are emitted by the target pass outwardly of the tube through thewindow in the form of a beam of radiation'which extends radiallythroughout an angle of 360 about the longitudinal axis of the unit asindicated by dotted lines in Fig. 1, the beam being restricted in sizein a direction axially of the device by the length of the window.

Electron bombardment of a target and consequent production ofX-radiation generates considerable heat in the anode 20. Therefore, todissipate such heat, the anode is provided with an enclosing finnedradiator 22 which carries a suitable thermostat 23. A suction type fan24 is located within the forward section 11 of the housing adjacentradiator 22 and is adapted to be operated by a conventional motor 25.When the fan is rotatedby the motor, cool air is drawn into the housingthrough a group of screened inlet openings 26 in housing section 12, andis directed through the fins of the radiator. In this way heat, which istransferred from the anode to the radiator, is dissipated. The resultantwarmed air is exhausted through a screened outlet 27 in section 11.

The fan and motor are preferably mounted as a unit I upon the wall ofsection 11 by suitable vibration dampens esaw nectin g the tube andother components to sources of electrical energy must likewise bepropelled or dragged along with the unit.

' The X-ray tube is preferably located in the rear section of thehousing and leads thereto may be readily connected to terminals,thereon, such as. terminal 29, without passing through the field ofX-radiation. However, the motor 25 and the thermostat 23 are located inthe forward'end of the unit. Therefore, leads which trail the unit as itprogresses along a pipe, must necessarily pass through the field ofX-radiation in order to be Connected to those components in the forwardsection.

Such extension of leads through a field of X-radiation normally resultsin the impression of images of the leads upon a radiograph,'which imagesmay result in confusion in the subsequent study of the radiograph, ormay even obliterate portions of the image of a weld.

In accordance with this invention, I have found it possible to provideelectrical conductors or leads which may be positioned within a field ofX-radiation without producing a readily distinguishable image in aradiograph.. In the shell 14 of the trailing section 12 of the housing Ihave mounted one end of a conduit 30 through whichleads 31 (Fig. 2)enter the interior of the housing. 'Leads 31 are connected to fixedterminals 32 mounted on the'inner Wallof the housing. Also fixedlymounted in spaced relation on the inner wall of the housing are a numberof insulating blocks 33, to each of which is secured one end of arespective X-ray transparent conductor 34.

The conductors 34 each comprise a strip of metal foil 35 formed'of X-raytransparent material such as aluminum, beryllium, magnesium, or otherselected material. The ends of the strips 35 are folded and interlayedwith small three-ply folded sheets 36 of copper or other conductivematerial, which thus form strong and rigid terminations for the foilstrips and by which the ends of theiconductors are enabled to besecurely connected to the insulating blocks 33 as by screws 37. Thestrips are connected by respective leads 38 to respective portions ofthe terminal device 32.

The other ends of the conductors are similarly interlayed withreinforcing sheets 36 and each carries a pair of fixed terminal pins oreyelets 39 to each of which is connected a small coil spring 40. Eachpair of springs 40 is connected to the ends of a small arm 41 which ispivotally connected to an insulating block 42 mounted on the inner wallof the housing 10 similarly to blocks 33. To each arm 41 is connected alead, one lead 43 extending to the thermostat and the other leads 44 tothe motor 25. e

The conductors 34 are thus disposed on and in spaced relation to theX-ray transparent shell 14. The springs 40 function to maintain thestrips 35 taut so that in each case a wide fiat surface will becontinuously directed toward the X-ray generating target 21.

The strips 35 must be formed thin enough so that the 'X-ray beam willpass through substantially unaltered.

I have found that if a shell 14 is formed of aluminum substantially 7thick, and the window 1? of nickel approximately .020" thick, then thestrips 35 may be of aluminum foil approximately .003 thick. Such stripsmay, of course, be comprised of two superimposed aluminnm foils .0015"thick.

In the structure shown in Fig. l, the X-ray beam passes through theannular window 19 and the tubular shell 14, whereby the beam isnecessarily modified to the extent that the window and shell absorb someof the radiation. Therefore, it is desirable that the conducting strips35 be characterized. by their ability to transmit substantia-lly thesame'portions of the X-ray beam that are; transmittedby the window orshell, or both.

For example, in Fig. 5 there is shown a curve 45 4 whichdiagrammatically illustrates the intensity and wavelength of an X-raybeam and wherein the height of the curve with respect to'line N depictsthe intensity, and the length of the curve parallel to line N indicatesthe wavelength. It is known that best results in radiography areobtained By htiliiing the hard intense rays which are found to :exist inthe'leading portion of a pulse. Curve 45 shows that a normal X-ray pulseproduces. hard intense X-ra'ys which, "after peak intensity isreachedptrail off 'as progressively softer and less intense r'ays, asindicatedby' the long gradual slope of the trailing portion of curve 45.

The X-rays, however, are modified by the window 19 as shown by curve '46whichillustrates the X-rays after passing through a window formed ofnickel ap proximately .020" thick. It will be noted that the peakintensity. of the X-ray beam is reduced only slightly but the softX-rays are reduced by a substantial amount. However, this reduction insoft X-rays is not of major consequence since, as stated above, the hardradiation is desirable.

In accordance with this invention, when X-rays pass through a conductingstrip '27, preferably made of alu minum foil .003" thick, the resultantcurve thereof will be substantially as shown by dotted line 47. Thisindicatesthat the peak intensity, or hard intense radiation, issubstantially unchanged by the strip and the soft radiation is reducedby a negligible amount.

Although aluminum foil is preferred as the material from which theconducting strips are made, materials such as beryllium, magnesium,or-others may be used, in which case it might be necessary to change thematerial of" either the window or shell, or both, so that thestripwill'not of itself alter the X-ray beam sufiiciently to produce an imagethereof on a radiograph.

Therefore, it is to be understood that the material of the conductingstrips and the thickness thereof may be balanced against the particularX-ray absorption characteristics of the window or shell or both so thatinsertion of the strips in the field of the X-ray beam will result insubstantially no additional attenuation of the beam.

I have further found that-an aluminum foil of approximately .003 thickand approximately one inch wide can satisfactorily conduct conventionallevels of currents necessary for efficient operation of devices such asblower fans, thermostats, etc. For heavier currents, the strips may bewidened accordingly without varying the thickness in accordance withthis invention.

From the foregoing it will be apparent that l have produced an X-rayunit adapted for use in radiographing, in a single exposure, annularsections of hollow 'bodies andcapable of producing high qualityradiographic pictures in which images of electrical conductors withinthe field of the X-ray beam are absent.

The embodiments of my invention herein shown and described are to beregarded as illustrative only, and it is to be understood that theinvention is susceptible to variation, modification, and change withinthe spirit and scope of the adjoined claims.

I claim:

1. In an X-ray unit comprising a hollow housing, an X-ray tube in thehousing for generating X-radiation and having a window for transmittingX-rays from the tube as a field of radiation, an electrical conductorextending parallel to the window in the field of radiation, saidconductor being an elongated flat strip of metal foil transparent toX-radiation located with one fiat surface directed toward the target ofsaid X-ray tube, and means for securely mounting the foil upon the wallof the housing' comprising a pair of spaced insulating blocks carried bysaid wall uponopposite' sides of the field of radiation, metal blockssecured to and interlocked with each end of thei;fold,; the metal ;blockat one endofthe1foil being secured to one of the insulating blocks, theother in- I we...

sulating block having an arm pivotally mounted thereon, and a pair ofsprings connecting opposite ends of the arm with transversely spacedportions ofthe other metal block, the springs maintaining the foil inposition relatively taut and rigid.

2. An X-ray unit as set forth in claim 1 wherein the housing contains atone end ,rnotor-operated cooling means for the X-ray tube and containselectrical connection means in the opposite end for connection to anexternal source of electrical power, and said electrical conductor isconnected at one end to the connection means and at its other end to thecooling means;

3. An X-ray unit as set forth in claim 1 wherein the housing contains atone end-electrical connection means for connection to an external sourceof electrical power,

the X-ray tube has an anode terminal located in the end of the housingopposite the connection means, and the electrical conductor is connectedat one end to the connection means and at its other end to the anodeterminal of the X-ray tube.

6 4. An X-ray unit as set forth in claim 1 wherein the conductor istransparent to only selected wavelengths of X-radiation.

References Cited in the file of this patent UNITED STATES PATENTS1,565,969 Spiro Dec. 15, 1925 1,975,880 Ulrey et al. Oct. 9, 19341,986,482 McKay Jan. 1, 1935 2,090,582 Mesick Aug. 17, 1937 2,222,549Verhoeif Nov. 19, 1940 2,259,037 Graves Oct. 14, 1941 2,502,429 ColeApr. 4, 1950 2,547,996 Boucher Apr. 10, 1951 2,663,812 Jamison et a1.Dec. 22, 1953 2,808,517 Cordingly Oct. 1, 1957 2,836,749 Atlee May27,1958 2,909,686 Zunick .1. Oct. 20, 1959 UNITED STATES PATENT OFFICECERTIFICATE OF CORRECTION Patent No. 2,980,600 I April 18, 1961 GottfridW. Steen It is hereby certified that error appears in the above numberedpatent requiring correction and that the said Letters Patent should readas corrected below.

Column 1, line 46, for "latter" read later column 4, line 74, for "fold"read foil (SEAL).

Attest:

ERNEST W. SWIDER Attesting Officer DAVID L. LADD Commissioner of PatentsUSCOMM-DC

